Engineering components often operate under complex loadings, in which the variable amplitude multiaxial stresses are raised by geometric discontinuities including holes, grooves, fillets and shoulders, etc. Besides, the non-proportional loading will lead to the rotation of maximum principal stress/strain and additional fatigue damage of structural elements in service. Consequently, the multiaxial and non-proportional loading have attracted increasing attentions. In this study, for distinguishing the effects of different load paths on fatigue life, a simple and applicable method to quantify the non-proportionality is defined, which comprehensively considers the influence of loadings on all material planes. A new equivalent strain damage parameter based on critical plane is proposed in this study. Specifically, to quantify the effect of non-proportional loading on fatigue damage, a non-proportional degree of loading on the generalized plane is developed. Coupling with the existing non-proportional coefficient, a novel fatigue damage parameter is derived by combining a non-proportional factor. Experimental data of 304 stainless steel, sintered porous iron and CuZn37 brass are utilized for model validation and comparison. Fatigue lives with different load paths are evaluated respectively. In comparison with the Fatemi-Socie (FS), Chen and Itoh models, proposed method more effectively evaluate the multiaxial fatigue life of materials under non-proportional loadings.

工程构件经常在复杂载荷下运行，其中变幅多轴应力由孔、槽、圆角和台肩等几何不连续性提高。此外，非比例载荷会导致最大主应力/应变的旋转和在役结构元件的额外疲劳损伤。因此，多轴和非比例载荷引起了越来越多的关注。本研究为区分不同载荷路径对疲劳寿命的影响，定义了一种简单适用的量化非比例性的方法，该方法综合考虑了载荷对所有材料平面的影响。本文提出了一种新的基于临界面的等效应变损伤参数。具体来说，为了量化非比例加载对疲劳损伤的影响，开发了广义平面上的非比例加载程度。结合已有的非比例系数，结合非比例因子推导出一种新的疲劳损伤参数。304不锈钢、烧结多孔铁和CuZn37黄铜的实验数据用于模型验证和比较。分别评估不同载荷路径下的疲劳寿命。与Fatemi-Socie (FS)、Chen 和Itoh 模型相比，提出的方法更有效地评估了材料在非比例载荷下的多轴疲劳寿命。通过结合非比例因子推导出一种新的疲劳损伤参数。304不锈钢、烧结多孔铁和CuZn37黄铜的实验数据用于模型验证和比较。分别评估不同载荷路径下的疲劳寿命。与Fatemi-Socie (FS)、Chen 和Itoh 模型相比，提出的方法更有效地评估了材料在非比例载荷下的多轴疲劳寿命。通过结合非比例因子推导出一种新的疲劳损伤参数。304不锈钢、烧结多孔铁和CuZn37黄铜的实验数据用于模型验证和比较。分别评估不同载荷路径下的疲劳寿命。与Fatemi-Socie (FS)、Chen 和Itoh 模型相比，提出的方法更有效地评估了材料在非比例载荷下的多轴疲劳寿命。